Duct Cleaning Information

Choosing a Duct Cleaner

Choosing a Duct Cleaner

In recent years millions of Americans have had their home air conditioning systems and ductwork cleaned. Duct cleaning can help to reduce the levels of dust within a home, increase the efficiency of the air conditioning system, and diminish the risks of indoor air pollution.



The National Air Duct Cleaners Association (NADCA), a non-profit organization, has published a guideline for consumers to follow When choosing an air duct cleaning company.NADCA offers these suggestions for selecting an air duct cleaner:




Make sure the cleaning contractor uses "source removal" cleaning methods designed to extract the debris within your air conditioning system. The routine application of encapsulants to seal debris within ductwork is not recommended. 

Get references from past jobs. Ask the duct cleaners customers if they were happy with the services performed, if they felt they benefited from the cleaning, and if they experienced any problems with their air conditioning system after the job. 

See if the duct cleaning company is a member in good standing of your local Better Business Bureau. 

Make sure the duct cleaner has worked on air conditioning systems similar to your own and ask how long the cleaning technicians who will be servicing your system have been performing duct cleaning. 

Make sure the duct cleaner takes care to protect your home and belongings. Duct cleaning is a relatively routine process and you should not have to do any unusual house cleaning after the job. 

Make sure that any chemicals used in the cleaning process are EPA registered for the intended application. You may also request a Material Safety Data Sheet (MSDS). 

Make sure that the cleaner you choose agrees to perform the cleaning services in accordance with all provisions of the industry performance standard NADCA 1992-01, Mechanical Cleaning of Non-Porous Air Conveyance System Components. 

Ask if the firm has all of the necessary business and professional licenses. Some states have recently passed statutes which require that air duct cleaners hold air conditioning contractors' licenses or similar professional licenses. 

Watch out for "add-on" sales. Some cleaners will charge a base fee and then surprise the customer with additional costs for applying sanitzers or other related services. Make sure you have agreed on the total cost and scope of the job before work begins. 

Confirm that the duct cleaner is a member in good standing of the National Air Duct Cleaners Association. Choosing a NADCA member to perform the work will ensure that your facility receives a thorough source removal cleaning in accordance with the association's mandatory performance standard. 


Contact the NADCA at:

1518 K Street, N.W., Suite 503, Washington, DC 20005; (202) 737-2926. The association provides free literature and listings of member firms. 

Do I need Duct Cleaning?

Do I need Duct Cleaning?

Knowledge about the potential benefits and possible problems of air duct cleaning is limited. Since conditions in every home are different, it is impossible to generalize about whether or not air duct cleaning in your home would be beneficial.


If no one in your household suffers from allergies or unexplained symptoms or illnesses and if, after a visual inspection of the inside of the ducts, you see no indication that your air ducts are contaminated with large deposits of dust or mold (no musty odor or visible mold growth), having your air ducts cleaned is probably unnecessary. It is normal for the return registers to get dusty as dust-laden air is pulled through the grate. This does not indicate that your air ducts are contaminated with heavy deposits of dust or debris; the registers can be easily vacuumed or removed and cleaned.


On the other hand, if family members are experiencing unusual or unexplained symptoms or illnesses that you think might be related to your home environment, you should discuss the situation with your doctor. EPA has published Indoor Air Quality: An Introduction for Health Professionals that can be obtained free of charge by contacting IAQ INFO at the number listed in this guide. You may obtain another free EPA booklet from IAQ INFO entitled The Inside Story: A Guide to Indoor Air Quality for guidance on identifying possible indoor air quality problems and ways to prevent or fix them.


You may consider having your air ducts cleaned simply because it seems logical that air ducts will get dirty over time and should occasionally be cleaned. While the debate about the value of periodic duct cleaning continues, no evidence suggests that such cleaning would be detrimental, provided that it is done properly.


On the other hand, if a service provider fails to follow proper duct cleaning procedures, duct cleaning can cause indoor air problems. For example, an inadequate vacuum collection system can release more dust, dirt, and other contaminants than if you had left the ducts alone. A careless or inadequately trained service provider can damage your ducts or heating and cooling system, possibly increasing your heating and air conditioning costs or forcing you to undertake difficult and costly repairs or replacements.


You should consider having the air ducts in your home cleaned if:


There is substantial visible mold growth inside hard surface (e.g., sheet metal) ducts or on other components of your heating and cooling system. There are several important points to understand concerning mold detection in heating and cooling systems: 

Many sections of your heating and cooling system may not be accessible for a visible inspection, so ask the service provider to show you any mold they say exists. 

You should be aware that although a substance may look like mold, a positive determination of whether it is mold or not can be made only by an expert and may require laboratory analysis for final confirmation. For about $50, some microbiology laboratories can tell you whether a sample sent to them on a clear strip of sticky household tape is mold or simply a substance that resembles it. 

If you have insulated air ducts and the insulation gets wet or moldy it cannot be effectively cleaned and should be removed and replaced. 

If the conditions causing the mold growth in the first place are not corrected, mold growth will recur. 


Ducts are infested with vermin, e.g. (rodents or insects); or


Ducts are clogged with excessive amounts of dust and debris and/or particles are actually released into the home from your supply registers.


Other Important Considerations...


Duct cleaning has never been shown to actually prevent health problems. Neither do studies conclusively demonstrate that particle (e.g., dust) levels in homes increase because of dirty air ducts or go down after cleaning. This is because much of the dirt that may accumulate inside air ducts adheres to duct surfaces and does not necessarily enter the living space. It is important to keep in mind that dirty air ducts are only one of many possible sources of particles that are present in homes. Pollutants that enter the home both from outdoors and indoor activities such as cooking, cleaning, smoking, or just moving around can cause greater exposure to contaminants than dirty air ducts. Moreover, there is no evidence that a light amount of household dust or other particulate matter in air ducts poses any risk to health.


EPA does not recommend that air ducts be cleaned except on an as-needed basis because of the continuing uncertainty about the benefits of duct cleaning under most circumstances. If a service provider or advertiser asserts that EPA recommends routine duct cleaning or makes claims about its health benefits, you should notify EPA by writing to the address listed at the end of this guidance. EPA does, however, recommend that if you have a fuel burning furnace, stove, or fireplace, they be inspected for proper functioning and serviced before each heating season to protect against carbon monoxide poisoning. Some research also suggests that cleaning dirty cooling coils, fans and heat exchangers can improve the efficiency of heating and cooling systems. However, little evidence exists to indicate that simply cleaning the duct system will increase your system's efficiency.


If you think duct cleaning might be a good idea for your home, but you are not sure, talk to a professional. The company that services your heating and cooling system may be a good source of advice. You may also want to contact professional duct cleaning service providers and ask them about the services they provide. Remember, they are trying to sell you a service, so ask questions and insist on complete and knowledgeable answers.


Indoor Environments Division (6609J)

Office of Air and Radiation (OAR)

EPA-402-K-97-002, October 1997 

Preventive Maintenance

Preventive Maintenance

Whether or not you decide to have the air ducts in your home cleaned, committing to a good preventive maintenance program is essential to minimize duct contamination.


To prevent dirt from entering the system:

Use the highest efficiency air filter recommended by the manufacturer of your heating and cooling system. 

Change filters regularly. 

If your filters become clogged, change them more frequently. 

Be sure you do not have any missing filters and that air cannot bypass filters through gaps around the filter holder. 

When having your heating and cooling system maintained or checked for other reasons, be sure to ask the service provider to clean cooling coils and drain pans. 

During construction or renovation work that produces dust in your home, seal off supply and return registers and do not operate the heating and cooling system until after cleaning up the dust. 

Remove dust and vacuum your home regularly. (Use a high efficiency vacuum (HEPA) cleaner or the highest efficiency filter bags your vacuum cleaner can take. Vacuuming can increase the amount of dust in the air during and after vacuuming as well as in your ducts). 

If your heating system includes in-duct humidification equipment, be sure to operate and maintain the humidifier strictly as recommended by the manufacturer. 

To prevent ducts from becoming wet:

Moisture should not be present in ducts. Controlling moisture is the most effective way to prevent biological growth in air ducts.


Moisture can enter the duct system through leaks or if the system has been improperly installed or serviced. Research suggests that condensation (which occurs when a surface temperature is lower than the dew point temperature of the surrounding air) on or near cooling coils of air conditioning units is a major factor in moisture contamination of the system. The presence of condensation or high relative humidity is an important indicator of the potential for mold growth on any type of duct. Controlling moisture can often be difficult, but here are some steps you can take:



Promptly and properly repair any leaks or water damage. 

Pay particular attention to cooling coils, which are designed to remove water from the air and can be a major source of moisture contamination of the system that can lead to mold growth. Make sure the condensate pan drains properly. The presence of substantial standing water and/or debris indicates a problem requiring immediate attention. Check any insulation near cooling coils for wet spots. 

Make sure ducts are properly sealed and insulated in all non-air-conditioned spaces (e.g., attics and crawl spaces). This will help to prevent moisture due to condensation from entering the system and is important to make the system work as intended. To prevent water condensation, the heating and cooling system must be properly insulated. 

Indoor Environments Division (6609J)

Office of Air and Radiation (OAR)

EPA-402-K-97-002, October 1997 

What is Duct Cleaning?

What is Duct Cleaning?

Most people are now aware that indoor air pollution is an issue of growing concern and increased visibility. Many companies are marketing products and services intended to improve the quality of your indoor air. You have probably seen an advertisement, received a coupon in the mail, or been approached directly by a company offering to clean your air ducts as a means of improving your home's indoor air quality. These services typically -- but not always -- range in cost from $450 to $1,000 per heating and cooling system, depending on the services offered, the size of the system to be cleaned, system accessibility, climatic region, and level of contamination.


Duct cleaning generally refers to the cleaning of various heating and cooling system components of forced air systems, including the supply and return air ducts and registers, grilles and diffusers, heat exchangers heating and cooling coils, condensate drain pans (drip pans), fan motor and fan housing, and the air handling unit housing (See diagram). On Top of Page. If not properly installed, maintained, and operated, these components may become contaminated with particles of dust, pollen or other debris. If moisture is present, the potential for microbiological growth (e.g., mold) is increased and spores from such growth may be released into the home's living space. Some of these contaminants may cause allergic reactions or other symptoms in people if they are exposed to them. If you decide to have your heating and cooling system cleaned, it is important to make sure the service provider agrees to clean all components of the system and is qualified to do so. Failure to clean a component of a contaminated system can result in re-contamination of the entire system, thus negating any potential benefits. Methods of duct cleaning vary, although standards have been established by industry associations concerned with air duct cleaning. Typically, a service provider will use specialized tools to dislodge dirt and other debris in ducts, then vacuum them out with a high-powered vacuum cleaner.


In addition, the service provider may propose applying chemical biocides, designed to kill microbiological contaminants, to the inside of the duct work and to other system components. Some service providers may also suggest applying chemical treatments (sealants or other encapsulants) to seal or cover the inside surfaces of the air ducts and equipment housings because they believe the sealant will control mold growth or prevent the release of dirt particles or fibers from ducts. These practices have yet to be fully researched and you should be fully informed before deciding to permit the use of biocides or sealants in your air ducts. They should only be applied, if at all, after the system has been properly cleaned of all visible dust or debris. 


Indoor Environments Division (6609J)

Office of Air and Radiation (OAR)

EPA-402-K-97-002, October 1997